The present invention relates to a universal joint for transferring motive force between a drive shaft and a driven shaft in equal speed.
Various universal joints for equivalently transferring drive power from a drive shaft to a driven shaft have been proposed and in practical use. A typical universal joint is constituted by a first joint, a second joint and a rolling element. The first joint includes a connecting shaft member connected to an output shaft of a reduction gear and an outer race member connected to the connecting shaft member. The second joint includes a transfer shaft interconnected with driven wheels and an inner race member connected to the transfer shaft and engaged with the outer race member through the rolling element. A popular production method of the first joint is disclosed in a Japanese Utility Model Provisional Publication No. 55-175627 in which a ring-shaped projection formed on an end surface of an outer race member is welded with a ring-shaped connecting portion of a connecting shaft member by means of friction welding. The welded portion is covered with a dust seal member to facilitate the removal of burr generated by the friction welding.
However, this joint obtained by the friction welding of two projections is required to further improve the productivity and the material efficiency without complicating the structure of the connecting shaft member.